Is there a way to test a gas valve on a roof top ac?
Seems to me that when I went to AC school ( about 30 years ago) there was a way to check the pressure at a valve using a manometer.
Is this possible are what?

Frank

Are you looking to just test pressures, or are you looking to test the gas valve for correct operation. If just pressures, there should be ports on the valve to hook a manometer to. One for inlet, one for outlet. If no ports on valve itself. There should be a port on the manifold(outlet side). You can check incoming pressure by adapting to the supply pipe.

I am trying to see if the gas valve is defective. Also want to know what the gas pressure is. Isn't it normally around 14 PSI?
That is what comes to mind.
Thank you

Natural gas inlet pressure should be between 5 and seven water column. Natural gas manifold pressure should be 3.5 water column.

Propane inlet, 11 to 15, manifold, 10. To check if gas valve is defective. Test for 24v at valve when valve is supposed to be open. If 24v is there, and valve doesn't open, then vavle is bad. If not 24v, then there is a problem elsewere that is not allowing correct voltage to gas valve. Hope this helps

Gas pressures will not be measured in psi at the valve.